Still a Mystery Squash

Last month, I blogged about a mystery squash that was growing in the garden.  At first I thought it was a watermelon, because the rind was pretty tough like a watermelon.  But in further investigation it didn't look like an ordinary watermelon.  It was from a volunteer plant and it looked like nothing I've ever grown before.  I assumed it came from my dad's compost, but he also said it wasn't anything he's grown or eaten. So where did the seeds come from?  He said that it might be from a bird or squirrel. I decided to harvest the squash because it was a good size and didn't know if it would get any bigger. 

I brought the squash to my parent's house because I know they would know how to cook it. I very rarely eat squash.

Inside the squash, it looks like a cucumber or zucchini, however, the skin is quite tough. The seeds are large like pumpkin seeds.  The flesh though is very firm, similar to a winter melon.  The flavor is very bland, almost flavorless.  Anyone have any idea what type of squash this is?